Knife sharpening mechanism



April 8, 1958 F. G. CLARK 2,829,474

' KNIFE SHARPENING MECHANISM .Filed June 17, 1957 2 Sheets-Sheet 1 INVENTOR.

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April s, 195s Filed June 17, 1957 F. G. CLARK KNIFE SHARPENING MECHANISM 2 Sheets-Sheet 2 KNIFE SHARPENING NIECHANISM Frederick G. Clark, Buffalo, N. Y., assignor to Eastman Machine Company, Buffalo, N. Y. Applieation June A17, 1951, serial N6. 665,894 6 claims. (c1. s1-z46) This invention relates to improvements in knife sharpening mechanisms for cuttingmachines of the type commonly used for cutting cloth and other sheet materials and in which the cutting is effected by a reciprocatory knife, such as disclosed in Patents No. 2,563,921 dated August 14, 1951 and 2,790,235 dated April 30, 1957.

Grinders for knife sharpening mechanisms of the type employing abrasive bands or belts have the belts arranged one above the other, and in order that the full length of the knife will be sharpened, the lower belt must be so mounted that when in its lower position it will be at least partly below the lower end of the knife so that the upper belt will move to the lower end of the knife. Since the belts are pressed into engagement with the knife by means of spring pressed lingers, the finger for the lower belt will move the part ofthe belt with which it engages beyond the position which it occupies when contacting the knife. Consequently, when the belt or band again moves upwardly relatively to the knife, itis necessary for` the lower end of the knife to push this belt back into position to engage the edge of the knife, against `the action of the spring urging the finger against the knife. Since this moving back of the belt and finger is done solely by the lower end of the knife against the abrasive face of the belt, it results in excessive grinding of the lower edge of the knife so that this end of the knife will become inoperative while the major length of the knife is still in good condition for cutting. y i

One of the objects of this invention is to provide a mechanism for avoiding the rounding or excessive grinding of the lower end of the cutting edge of the knife while sharpening the same. Another object is to provide mechanism for limiting the movement of the presser finger of the belt beyond the position which it occupies when sharpening a knife, so that when the belt is belowthe lower end of the knife, the knife will not be forced to return the belt and presser finger against the spring acting on the presser finger into its normal knife sharpening position thereby materially increasing the useful life of the knife;

Other objects and advantages will be apparent from the following description of` some embodiments of the s invention, and the novel features will be particularly pointed out hereinafter in connection with the appended claims. j

In the accompanying drawings:

Fig. 1 isa side elevation of the lower portion of a cloth cutting machine having s improvements embodying this invention applied thereto.

Fig., 2 is a sectional "plan view thereof on line 2&2,

- reciprocates the knife 23 in a vertical guide" at the front 2,829,474 N Patented Apr. 8, 19581 ICC Fig. 6 is an elevation onan enlarged scale of a clamp-'i-` ingarm` used` in connection with my improvements.

I have illustrated in the accompanying drawings my improvements as applied by `way of exampleto a cutting machine similar tothe one shown in said Patents` #2,563,921 and #2,790,235. This machine comprises` the yusual base 20 adapted to rest on and to be moved about on a table which supports the lay `of material to be cut. An upright, `slender standard 21 is rigidly secured on the baseand rises upwardly therefrom and supports the stationary frame 22 of an electric motor which of the standard ,21 through suitable driving mechanism (not shown). `25` representsjthe usual presser foot ar` ranged on the lower end of a guide bar 27 which extends vertically in front of the knife and is suitably mount-V ed for vertical adjustments on the machine to set the` s presser `foot at different levels according to the thickness of different lays orpiles of material. t The knife ingthe ,particular machine illustrated in` the drawings is sharpened by grinding means comprising two 1narrow abrasive bands or belts `30 and 31 which are dist .employedpthe spring which presses the lower belt against" posed at opposite sides of the knife to travel cr'o'sswise of the same in contacttwith the opposite sides of the knife edge, and these belts pass around two front drive pulleys 32 and 33 and rear spring-pressed belt tensioningpulleys t 34 and 35 in the direction indicated by the arrows 37, Fig. 3. These belts are power-driven `by the knife-operating motor and are mounted `on the underside of a grinder carriage 36 arranged to move up and down lengthwise of the knife edge to` enable the belts to sharpen the knife edge throughout its full length. This carriage: 36 together with the various parts mounted thereon is movable vertically relatively to a housing or cover piece 38 which is removably secured in place on `the motor frame 22 at the front ofthe machine and encloses parts of the knife operating and sharpening mechanisms. `The grinder carv` riage may be mounted and guided in its up and down movements in any suitable or desired manner, for example, as disclosed in said Patent #2,563,921 and an earlier Patent #2,183,786 issued December 19, 1939 to Eastman Machine Company, assignee.

In the construction illustrated by way of example, the drive pulleys 32 and 33 are fixed on the lower endsV of two vertical shafts 40 and 41` which are rotatable and held against axial movement relatively to the carriage 36 so that these `shafts may move up and down with the carriage. These shafts are rotated by intermeshing pinions l(not shown) arranged in the housing part 38 of the machine and suitably driven from the motor as has here-` tofore been customary.

Themechanism for producing the up and down travel of the grinder carriage 36 and the parts mounted thereon along the knife edge preferably includes a screw shaft 44 having `crossing right and left hand threads and which is suitably rotated, for example through gearing, not

shown (in broken lines in Fig. 3), connectingthe screw shaft with the shaft 41, as in the patents hereinbefore mentioned. As the screw shaft is rotated it moves downbelts arranged one above the other, it is necessary that` the upper belt moves down to the lower end of the knife and consequently the lower belt must move beyond the lower end `of the knife. In constructions heretofore the cutting edge of the knife will, when it reaches the bottom of the knife, move the belt beyond the position which it occupies when the knife is being sharpened. Consequently, when the belts move upwardly with "relation to the knife, the knife must press against the abrasive face of the lower belt suciently to "move vit back into proper position for engaging the cutting edge of the knife, and this results in materially greater wear` or abrasion on the lower end of the knife than on 'other parts thereof so that the knife will have to be discarded and replaced while the upper portions of the 'same 'are still in good condition for cutting.

The two abrasive belts are urged against `theedge of the knife by means of shoes A50 pivotally mounted at 51 on the grinder carriage 36. Each shoe has a part extending adjacent to the cutting edge of the knife which is provided with a presser finger 52. The end of each presser yfinger is provided with a button-like projection or pad 53 which is shaped to press against the inner face of the belt and urge the outer'or abrasive surface of the belt into sharpening contact with lthe cutting edge of the knife. The shoe is yieldingly urged by means of a spring 54 in a direction to cause `the shoe to swing about its pivot 51 to move the presser finger toward the belt. The spring in the construction shown is 'of approximately U-shape having one end 55 extending into a hole drilled in the carriage 36 and extending about the pivot 51 with its other end bearing against vthe presser linger. Consequently it is obvious that when the lower belt 36 passes beyond the lower end of the knife, the spring 54 will move the presser linger somewhat farther than the position which it occupied while its belt engaged the knife, so that the portion of the belt engaged by this presser finger will be below the lower Dend of the knife.

As is common in the construction of knife sharpen`q ing devices of this type, each presser 4linger is so formed as to engage when in its upper position with a spreader member 57 ext-ending downwardly from the lower portion of the frame of the cutting machine. The lower end of this spreader member has inclined sides, see particularly Figs. `3 andr 4, which engage portions of the shoe 50 when in their upper positions, thus forcing the shoes apart by a wedging action so that the belts will be out of engagement with the knife, which is the position of -the belts when the knife sharpening mechanism is not in use.

When the grinder carriage moves downwardly from its inoperative position the shoes, 'on moving out of en gagement with the bevelled lower surfaces at the lower end of the spreader member 57, will be moved by the springs 54 into positions in which the presser fingers will move the belts into sharpening engagement with opposite sides of the cutting edge of the knife.

In accordance with my invention, I provide means which engage the lower shoe 50 after it lhas moved its belt into engagement with the knife adjacent to the upper part of the travel of the shoe so that'the shoe will be prevented from moving beyond the position which it occupies when sharpening the knife. In the construction shown for this purpose I have provided a clamping arm 60 which is pivoted at 61 on a lug or extension projecting rearwardly from the grinder carriage. This clamping arm has an upwardly extending part or arm 62 which yextends into position to engage the spreader member 57, this spreader member for that purpose being preferably provided on the lower part of its front side with aninclined face 63. The clamping arm is also provided with a friction surface 64.which extends into a position to engage a corresponding friction face formed on an extension or arm 65 preferably formed integral with the shoe 50 for the lower belt. The 'contacting friction or clamping faces of the arms 65 and the part 64 of the clamping member may be serrated, roughened or left smooth so that there will .be sufficient friction to prevent relative lmovement of the parts 64 `and 65. The clamping arm is urged by means of a spring 66 into a position in which the surface 64 of the clamping arm engages the extension 65 of the shoe as shown in Fig. 3. This upwardly extending arm 62 extends upwardly to a greater extent than the spreader engaging parts of the shoes so that the surface '64 and the arm 65 will be held out of engagement for a shortl interval of time after the shoes have been moved into their presser fingers operative or grinding positions. Immediately after the shoes have moved the belts to this position, the clamp will engage the arm 65 of the shoe and thus prevent the shoe from being moved by lthe spring 54 beyond the position which it occupies during the sharpening of the knife. Consequently, when the lower belt moves downwardly beyond the lower end of the knife, the belt will remain approximately in the same position which it. occupied during lthe sharpening 'of the knife. Consequently when the lower belt moves upwardly with relation to the knife, the knife will not be required to force the abrasive belt and the shoe into their sharpening positions since they will already be in such positions. Therefore the excessive abrasion which has heretofore taken place on the lower end of the knife is eliminated and by actual test it has been found that this approximately doubles the useful life of the knife.

One advantage of the construction described is that it requires no adjustment to enable it to operate properly on knives, whether they are new lor whether the cutting edge has been ground back to a considerable distance, since lin any case the clamp will hold the presser finger against further movement when below the end of the knife.

Another advantage is that the mechanism greatly reduces the possibility of having the lower edge of the knife cut the lower belt.

It will be understood that various changes in the details, materials and arrangements of parts, which have been hereindescribed and illustrated in order to explain the nature of the invention, may be made by those skilled in the art, within the principle and scope of the invention, as expressed in the appended claims.

I claim:

l. A knife sharpening mechanism for cutting machines having a knife guided for reciprocal movement, a grinder carriage movable up and down along said knife, an abrasive knife sharpening belt mounted on said carriage in operative relation to the cutting edge of said knife, a presser finger mounted `on said carriage adjacent to 'said cutting edge, means also mounted on lsaid carriage and yieldingly urging said presser finger against said belt for pressing said belt against saidcuttng edge, and a member 0n said carriage which is movable into engagement with said yielding means when urging said presser finger into engagement with said belt to limit the movement of said presser -finger by said means when said belt is belowI the lower end of said knife.

l2. A knife sharpening mechanism for cutting machines having a knife guided for reciprocal movement, a grinder carriage movable up and down along said knife, an abrasive knife sharpening belt mounted on said carriage in operative relation to the cutting edge of said knife, a pressure finger mounted in position to engage said ybelt yand move the same into engagement with said cutting edge, a shoe pivoted on said carriage and on which said presser finger is mounted, resilient means engaging said shoe and urging the same to swing in a direction to press said vfinger against said belt, and a member movable into engagement with said shoe when said finger urges said belt against said edge to prevent further swinging of the same whensaid belt is below said knife.

3. A knife sharpening mechanism for cutting machines having a knife guided for reciprocal movement, a grinder carriage `movable up and down along said knife, an abrasive knife sharpening belt mounted on said carriage in operative relation to the cutting edge of said knife, a pressure finger mounted in position to engage said belt and move the same into engagement with said cutting edge, a shoe pivoted on said carriage and on which said presser finger is mounted, resilient means engaging said shoe and urging the same to swing in a direction to press said finger against said belt, a clamping member movable into engagement with said shoe after the same is in position in which it presses said belt against said knife, and a tixed part on said machine which moves said clamping member out of engagement with said shoe when said carriage is in its upper position.

4. A knife sharpening mechanism for cutting machines having a knife guided for reciprocal movement, a grinder carriage movable up and down along said knife, an abrasive knife sharpening belt mounted on said carriage in operative relation to the cutting edge of said knife, a pressure finger mounted in position to engage said belt and move the same into engagment with said cutting edge, a shoe pivoted on said carriage and on which said presser finger is mounted, resilient means engaging said shoe and urging the same to swing in a direction to press said finger against said belt, a clamping member movable into enngagement with said shoe after the same is in position in which it presses said belt against said knife, a wedge member which moves said shoe out of belt pressing position when said grinder carriage is in its upper position to move said belt out of engagement with the knife, and cooperating parts on said clamping member and said wedge member which move said clamping member out of engagement with said shoe when said grinder carriage is in its upper position and which releases said clamping member to engage said shoe after said shoe engages said belt.

5. A knife sharpening mechanism for cutting machines having a knife guided for reciprocal movement, a grinder carriage movable up and down along said knife, an abrasive knife sharpening belt mounted on said carriage in operative relation to the cutting edge of said knife, a shoe mounted on said carriage adjacent to said knife and having a part extending into position to engage a belt for pressing the same against said knife, yielding means urging said shoe into position to engage said belt,

means cooperating with said shoe for moving the saine out of belt engaging position when said carriage is at the upper end of its path of movement, and for releasing said shoe to move into belt engaging position after said carriage has moved downwardly, and a clamping member movable into engagement with said shoe to stop further movement of the same relative to said knife after said shoe has moved into engagement with said knife.

6. A knife sharpening mechanism for cutting machines having a knife guided for reciprocal movement, a grinder carriage movable up and down along said knife, an abrasive knife sharpening belt mounted on said carriage in operative relation to the cutting edge of said knife, a shoe pivotally mounted on said carriage, a presser finger on said shoe extending into position to engage a belt, yielding means acting on said shoe to swing the same into position to urge said presser finger into engagement with said belt for pressing the belt against the cutting edge of said knife, a wedge member mounted on said machine and having an inclined surface in position to engage said shoe to move the same into a position in which said finger is out of engagement with said belt when said carriage is in its upper position and releasing said shoe when the carriage moves downwardly from its upper position to permit said finger to engage said belt, a clamping member also mounted on said carriage and having a part movable into clamping engagement with a part of said shoe to prevent movement of said shoe by said yielding means, said clamping member having a part eX- tending upwardly into position to engage said wedge member to move said clamping member out of engagement with said shoe before said shoe engages said wedge, said upwardly extending part of said clamping member moving out of engagement with said wedge member after said shoe has been moved out of engagement with the same to permit said clamping member to engage said shoe after the shoe has moved into position to cause said finger to engage said belt.

References Cited in the file of this patent UNITED STATES PATENTS 2,281,023 Clark et al. Apr. 28, 1942 

